Corrosion inhibitor composition



CORRGQGN ENEEEBIT R COMPOSITION Clarence A. Weltrnan, Niagara Falls, N.Y., assignor to Aiox Corporation, Niagara Falls, N. Y., a corporation ofNew York No Drawing. Application June 9, 1954 Serial No. 435,626

4 Claims. (Cl. 252-77) This invention relates to water-solublecorrosion-inhibiting compositions and is more particularly concernedwith inhibitors for use primarily in water circulating systems such asautomobile radiators, certain industrial heat exchangers, cooling towersand the like.

The requirements of a good water-soluble corrosion inhibitor can besummarized as follows:

(a) It shall protect steel or iron from the normally corrosive action ofhard or soft water containing normal amounts of dissolved oxygen or air.

(b) It shall not attack or corrode other metal normal- 1y used incirculating systems, such as copper, brass, aluminum, lead or sloder.

(c) It shall be completely water-soluble.

(d) It is desirable, also, that it besoluble in alcohols (methanol,ethanol) and ethylene glycols in the required concentrations.

(e) It is desirable that the inhibitor provide some residual protectionof the metal after it is removed from contact with the inhibited water.Thus, if some water evaporates from a cooling bath or system; theexposed metal should be protected for a short time. Uninhibited waterwill cause corrosion While in contact with the steel and will acceleratefurther corrosion as it evaporates.

It has been found that a corrosion inhibiting composition havingoutstanding properties may be prepared by blending about equal parts ofpara tertiary butyl benzoic acid, hereinafter referred to as ptBBA, withrelatively high molecular weight aliphatic carboxylic acids derived froma petroleum fraction, e. g., from a normally liquid petroleum fractionsuch, for instance, as 36-40, distillate, by liquid-phase, controlledpartial oxidation of the same according to the process disclosed in U.S. Patents Nos. 1,690,768 and 1,690,769 to Arthur W. Burwell, andcompletely neutralizing the tree acids present in the resulting mixtureby treating the latter, at an elevated temperature not substantiallyhigher than 100 C., with a suitable organic amine such for example asdiethanolamine,, triethanolamine, mixtures of these amines, morpholine,and the like.

As disclosed in the aforesaid Patents Nos. 1,690,768

and 1,690,769, the acids content of the oxidate is removed from thelatter by saponification and subsequent acidification. Said acids are,in major portion, aliphatic carboxylic acids ranging in carbon chainlength from C to C with a mean length of C The acids content may, andusually does, include in minor proportion straight and branched chainaliphatic hydroxy carboxylic acids having substantially the same carbonchain length.

The neutralization reaction, being exothermic, must be so conducted thatthe temperature of the reaction mixture does not rise more than a few-e.g., two or three-degrees above 100 C. Control of the rate at which theorganic amine is added to the hot mixture affords a suitable mode ofcontrol of temperature rise. Also, the pres ence in the mixture, towhich the organic amine is being added, of a substantial but minorproportion of water aids i 2,832,742 Patented Apr. 29, 1958 inmaintaining the temperature at approximately 100 C. during theneutralization. The presence of water efiects the further advantage thatthe reaction mixturewhich, in the absence of water, is or may be viscousand which may tend to crystallize on standing at room temperaturetherebyis given a desirable fluidity for ease of handling.

The resulting completely neutralized reaction mixture is soluble inWater in practically all proportions, and is soluble also in methanol,ethanol, ethylene glycols and other commonly employed alcoholicanti-freeze agents. It can be added directly to the water of the systemto be protected; or it may be dissolved in an alcoholic antifreeze agentand added to the water circulating systems in the dissolved form. Inindustrial water circulating systems the additive of the presentinventionwhether added directly or as a solution inanti-freeze--normal1y is used in an amount to yield a concentration offrom 0.1 to 1.0% by weight of the system to be protected.

SPECIFIC EXAMPLE A typical preparation illustrative of the presentinvention is prepared as follows, all percentages being by weight:

a. Blend: Alox 37.5% oxidized petroleum acids 425=375 g. 37.5%.ptBBA=375g.

25.0% water=250 g.

0. Stir until cool (not essential) The final composition is, then, areaction mixture of:

27.1% Alox 425 27.1% ptBBA 27.7% diethanolamine 18.1% water By theexpression oxidized petroleum acids Alox 425 as used above applicantmeans the mixture of aliphatic carboxylic acids, ranging in carbon chainlength between C, and C and having a mean carbon chain length of Cderivable from an oxidate of 3640 petroleum distillate.

The product, prepared as above described, is completely soluble in waterand in commonly employed alcoholic anti-freeze agents. When dissolved inwater in an amount to give a concentration of 0.1 to 0.1% (a 0.2%concentration being usual, it protects steel, or iron, from the normallycorrosive action of water containing a normal amount of dissolved oxygenor air; moreover, it provides residual protection of the metal after thelatter has been removed from contact with the inhibited water. It has nosignificantly detrimental effect on copper, brass, alumi num, lead orsolder. It is efiective at from room temperature to at least 160 F., andin water having a pH of from 6 to 10.

VARIABLES IN PREPARATION or INHIBITOR 1. Effect of components glycols;and, the amine-neutralized ptBBA per se is a" less etiective corrosioninhibitor at elevated temperatures, besides being expensive. Theamine-neutralized, approximately 50-50, mixture of ptBBA and oxidizedpetroleum acids combines the advantages of full range of solubilities,performance at elevated as well as low temperatures, limited attack onlead, copper and brass, and desirably low cost. Where alcohol solubilityis not required, the proportion of ptBBA to petroleum acids may belowered, e. g., to -80 or to a ratio intermediate these extremes.

In lieu of the oxidized petroleum acids referred to above red oil (oleicacid) has been found to be an operable although not preferred component.A 50 50 blend of red oil and ptBBA when 100% neutralized withdiethanolamine was found to be elfective, in water, at concentrationsabove 0.5 This suggests that other relatively high molecular weightorganic acids may have at least limited effectiveness.

It does not appear that the ptBBA can be replaced with Worthwhileresults; Thus, benzoic acid substituted for the ptBBA yielded a greatlyinferior .product.

As was suggested above, either triethanolamine or morpholine can besubstituted for diethanolamine with fair effectiveness.

2. Efiects of temperature The neutralization of the mixture of ptBBA andoxidized petroleum acids may be carried out at any temperature betweenabout and 100 C. If the temperature is permitted to rise appreciablyabove 100 C., amides rather than amine complexes or salts tend to 'beproduced, which amides are insoluble or only poorly soluble in water. Asto the observance of temperatures substantially below 100 C., it is tobe noted that effective inhibitors have been prepared at 25 C., C., C.,and C. However, because the temperature rise, due to the exothermicityof the reaction, is difi'icultly controllable when the reaction isstarted, at lower temperature, it seems preferable to control thetemperature during neutralization at about C.

3. Effect of degree of neutralization The degree of neutralization ofthe acids is critical in terms of meeting all of the requirements setforth for a good inhibitor.

The amount of amine to use for complete neutralization (called 100%) isas follows:

The ASTM acid number of the blend of oxidized petroleum acids, e. g.,Alox 425, and ptBBA is calculated as follows:

Acid No. ptBBA=3l5 (calculated from molecular weight or determined) AcidNo. Alox 425=l80 (determined) Therefore, a 50- 50 blend has an acidnumber of 50% of 3l5=l57.5 50% of 180: 90.0'

Combined acid No.=247.5

When 1000 g. of this is neutralized directly, the calculation fordiethanolamine is:

Mol. wt. KOH= 56.1 Mol. wt. DEAL-105.1 x=464 g. DEA per 1000 g. mixedacids calculated from any other combination of ptBBA and ill Te's't'shave been performed in which as much as 13% excess of diethanolamine hasbeen added. The resulting product is hazy and tends to separate a slightclear layer. The product containing an excess of amine is essentially asefiective a corrosion inhibitor as the normal product, but is wastefulof amine and yields a. physically unstable product.

Products have also been prepared in which only 75 of the theoreticalamount of amine has been used. Such products are effective protectiveagents, butshow mild corrosion of lead, copper and brass.

Thus, the optimum range of neutralization is 95-103 Complete, or 100%neutralization is preferred. 7 To repeat, a wide range of degress ofneutralization is possible to yield products which protect steel.However, increased attack of non-ferrous metals occurs at less than 100%neutralization, and a loss of clarity of product occurs when an excessof amine is used.

TEST PROCEDURES AND RESULTS 1. Immersion test-Corrosion of steel This isa static test in which a 2" x 4" cold rolled steel panel, with asand-blasted surface, is immersedih the. test solution. The panel isexamined daily for evidence of rusting, staining or other visible signsof corrosion.

The steel panels are tested in solutions of the inhibitor in tap water.In addition panels are tested at a range of solution pH values. Thus,to'the solution of inhibitor in tap water, HCl is added to adjust the pH(4 or 6 in the tests). Other solutions are adjusted with concentrated NHOH to pH values of 8 and 10.

In addition to static tests at pH 4, 6, 7.6 (pH of inhibi tor in tapwater), 8, 10 at temperature (77 F.), a'similar series is run, at F.Thus protection tests were run a at varying pH and at two temperatures.

2. Rotating metals test This test Wasdesigned to determine the eifect ofmoving water over various metals. It is hoped that this test willsimulate actual conditions in a circulating system.

One inch squares of metal with holes drilled through their centers areweighed and then suspended on a brass rod. 'Each metal square isseparated from the others by a As'fthick brass washer. The test metalsare copper, brass, brass with a /2" diameter solder spot, lead,magnesium, steel and cast iron.

The brass rod and test metals are immersed in the test solution at 160F. and rotated at 500 R. P. M. for two weeks. At the end of that periodeach metal is cleaned, examined for staining, etc., and then re-weighed.The weight loss per square centimeter of surface is calculated.

3. Residual protection test This test is designed to determine whethersteel will be protected after removal from contact with inhibited water.A sand-blasted panel is immersed in the test solution, removed andallowed to drain for one hour. It is then stored in a static humiditycabinet which is essentially a 4. Test results Selected test data aresummarized in the following tables, in which Table 1' compares corrosionprotection versus degree of neutralization, and Table II comparestemperatures at which the product was prepared.

TABLE I {Corrosion protection versus degree of neutralization]Composition Corrosion tests (Days to fail) React Percent of Percent Std.Residual Code Designation Temp, theory additive pH,* Protec- PercentPercent Percent C. Ncutralized in Water R.- l. Std. pH 4 pH 6, pH 8, pH10, tion ptBBA 425 Water pH,* @160" 160 F. 160 F. 160 F. (Days) OP-l-lll37. 5 37. 5 25. 100 13 XS OP-l-lll 37. 5 37. 5 25. 0 100 75999992-9999999999 DIN l-OoOlmMHOmwMl-Q oo coon-cocoon Standard pH refersto the pH resulting from dissolving the inhibitor in tap water withoutaddition of H01 or NHAOH. The pH of such solutions is approximately 7.6.

TABLE II [Preparation temperature versus corrosion protection] PercentCorrosion tests (Days to Fail) Code of theory React Percent Std. %H,

Designation Neutrai- Temp., inWater R ized 0. Std. pH, p114, pH 6, pH 3,pH 10, 100 F. 160 F. 160 F. 160 F. 100 F.

3'22 1 01 00+ 17 1 1 24+ 0. 30 60+ 30+ 0.05 1 2 0r-1-119A-- 100 so 0. 1060+ 4 0.20 60+ 0.05 1 OP-l-ilQB.-. 100 0. 10 60+ 4 Iclaim: and a highmolecular weight aliphatic carboxylic acids 1. A water-soluble corrosioninhibiting composition for mixture derived from an oxidized petroleumfraction, said use in aqueous liquid systems, in contact with ferrousand aliphatic carboxylic acids having carbon chain lengths non-ferrousmetals, consisting essentially of substantially between C and C and amean carbon chain length completely neutral diethanolamine salts ofabout equal of C parts by weight of para tertiary butyl benzoic acid and3. The composition defined in claim 1, in which the oxa high molecularweight aliphatic carboxylic acids mixidized petroleum fraction is anoxidized 36-40 distillate ture derived from an oxidized petroleumfraction, said of petroleum origin.

aliphatic carboxylic acids having carbon chain lengths 4. The coolantcomposition defined in claim 2 in which between G; and C and a meancarbon chain length said medium is a solution of alcohol in water. OfC14.

2. A liquid coolant composition for use in contact with e c s ted in thefile of this patent ferrous and non-ferrous metals, characterized inthat the UNITED STATES PATENTS same 1s a solution in aqueous medium offrom about 0.1% to about 1.0% by weight of a water-soluble corrosion2:330:524 sPlelds p 1943 inhibiting composition consisting essentiallyof substan- ,949 Lleber June 27, 1950 tially completely neutraldiethanolamine salts of about 2,578,654 Hearne et a1. Dec. 18, 1951equal parts by weight of para tertiary butyl benzoic acid 2,629,649Wachter et al. Feb. 24, 1953

1. A WATER-SOLUBLE CORROSION INHIBITING COMPOSITION FOR USE IN AQUEOUSLIQUID SYSTEMS, IN CONTACT WITH FERROUS AND NON-FERROUS METALS,CONSISTING ESSENTIALLY OF SUBSTANTIALLY COMPLETELY NEUTRALDIETHANOLAMINE SALTS OF ABOUT EQUAL PARTS BY WEIGHT OF PARA TERTIARYBUTYL BENZOIC ACID AND A HIGH MOLECULAR WEIGHT ALIPHATIC CARBOXYLICACIDS MIXTURE DERIVED FROM AN OXIDIZED PETROLEUM FRACTION, SAIDALIPHATIC CARBOXYLIC ACIDS HAVING CARBON CHAIN LENGTHS BETWEEN C7 ANDC18 AND A MEAN CARBON CHAIN LENGTH OF C14.